Utility power disturbances and momentary power interruptions degrade power quality and can adversely affect the operation of sensitive electronic equipment. Even momentary interruptions of just a few cycles can result in unscheduled controller resets, shutdown of a factory assembly lines, loss of computer data, etc. Thus, loss of electric power for only a short time can be detrimental by factory downtime, product damage and reduced productivity, etc.
The solution is to provide a system that continuously monitors power quality for power outages, momentary interruptions, voltage sags and swells, and switches sensitive loads from the utility service to an alternate standby power source when a power disturbance is detected. It is desirable that the switching take place as quickly as possible so sensitive electronics in the critical load are not affected.
Prior art methods of detecting voltage fluctuations and momentary interruptions include the template method and the three-phase to two-phase transformation methods. These methods can be inaccurate and are not as robust as the present invention.